Question

If m(x) = x3 and n(x) = √ 6 + x , find the function value, if possible.

(m – n)(–5)

A. 124
B. –124
C. Not a real number
D. –126

Answer 1

The correct answer is option D. -126

Explanation:

Points to remember

Composite functions

f(x) and g(x) be the functions then,

(f - g)(x) = f(x) - g(x)

To find the value of (m - n)(-5)

Let m(x) = x³ and n(x) = √ (6 + x)

(m - n)(x) = m(x) - n(x)

= x³ - √( 6 + x)

(m - n)(-5) = m(-5) - n(-5)

= x³ - √( 6 + x)

= (-5)³ - √( 6 + -5)

= -125 - √1

= -125 -1

= -126

The correct answer is option D. -126